The invention relates to “active implantable medical devices” as defined by Directive 90/385/EEC of 20 Jun. 1990 of the Council of the European Communities, specifically implants to continuously monitor heart rhythm and deliver to the heart, if necessary, electrical pulses for stimulation, resynchronization and/or defibrillation in case of rhythm disorder detected by the device.
The invention relates more particularly to devices in the form of an autonomous capsule implantable in a heart chamber (ventricle, atrium or even the arterial left heart chamber), hereinafter referred to as “autonomous capsule” or “leadless capsule”. These capsules are devoid of any physical connection to a main implantable device (such as the housing of a pacing pulse generator) or non-implantable device (external device such as a programmer or a monitoring device for remote monitoring of the patient). They are referred to as leadless capsules therefore, to distinguish them from the sensors or electrodes located at the distal end of a conventional probe (lead), covered along its length by one or more conductors galvanically connecting the electrode or the sensor to a generator which is connected to an opposite proximal end to the lead.
However, as will be understood from the description herein, the autonomous nature of the capsule is not inherently a necessary feature of the invention, and that the latter can be applied to capsules permanently mounted at the distal end of a lead.
To hold the leadless capsules in place after implantation, they are provided with an anchoring element, usually having a projecting helical screw extending axially of the capsule body and adapted to penetrate the heart tissue at the implantation site by screwing, according to a similar method as for conventional screw leads.
EP 2394695 A1 (Sorin CRM SAS) describes such a type of screw leadless capsule and its accessory for the implantation at the selected site by docking of the axial screw and rotary drive of the capsule to secure it to the heart wall, wherein it will be maintained by the anchoring axial screw. Similar systems have been proposed implementing needles, hooks, barbs, etc., these anchoring members extending the capsule at its distal end so as to penetrate the tissue and anchoring the capsule from this end.
Regarding the capsule itself, it is generally cylindrical with a length between 20 to 40 mm in the case of leadless capsules, this cylindrical form being dictated by the access route via the peripheral venous system.
The configuration as described above (cylindrical body and axial anchorage) is compatible with implantation in the region of the apex, at the base of the ventricle, but can cause a number of problems for other implantation sites, for example on the ventricular or the atrial septum. Indeed, the small width of the right ventricular cavity, combined with the heartbeat, may cause deleterious repeated contact of the proximal portion of the capsule with the free wall of the heart muscle, the tricuspid valve or the pillars. Moreover, the area of the apex is not always the best target site for certain therapies, and may pose a risk because of the thinness of the wall in adjacent areas, creating a significant risk of perforation by the anchoring member during the implantation operation.
A further difficulty is that the implantation accessory (as described in the aforementioned EP 2394695 A1) generally places the capsule with its main axis in the extension of a catheter or of a stylet of the accessory, so as to go through the peripheral venous system and direct the capsule to the implantation site. For directing the capsule towards the apex of the ventricle, such an accessory is very suitable and can accurately be delivered and fully secured to the selected implantation site. Then the capsule can be anchored and then disconnected from the implantation accessory.
However, if it is desired to implant the capsule for example on the septal wall or on the right atrium wall, in order to anchor the screw it is necessary to perpendicularly access this wall with the capsule. This involves having a system with an adjustable head, especially complicated to handle with the heart beat because the head capsule is not naturally directed to the site of implantation, because of the elongate tubular shape of the capsule. To reduce this risk, flattened capsules have been proposed, for example EP 2537555 A1 (Sorin CRM SAS), the implementation of which is, however, more complex than that of tubular elongated capsules because their shape is not naturally suited for the passage in a vessel.
Various exemplary embodiments as disclosed herein propose an elongate tubular capsule, notably of the leadless type, specifically adapted for implantation on the interventricular septum or any other wall, including the thin or thick walls of the different heart chambers.